JP2988176B2 - Automatic arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic arc welding method, and more particularly to an automatic arc welding method for performing arc welding while estimating a discharge state based on an arc generation confirmation signal.

[0002]

2. Description of the Related Art Conventionally, a method of automatically performing arc welding using a robot or the like has been known. In such an automatic arc welding method, it is necessary to start and stop the arc discharge and move and stop the welding torch and the like in synchronization with each other.

Here, the movement and stop of the welding torch or the stop of the arc discharge can be substantially synchronized with a control signal for controlling them, and there is no problem. However, the start of arc discharge requires some time until the discharge is formed, and furthermore, the discharge may not be formed due to the state of the work or the like. And the discharge start timing is not always synchronized.

That is, in order to synchronize the start time of the arc discharge with the operation time of the welding torch or the like, it is necessary to provide a mechanism for detecting the start of the arc discharge, and to synchronize based on the detection signal. is there. For this reason, equipment that employs such an automatic arc welding method generally includes a mechanism for generating an arc generation confirmation signal (WCR signal) and a mechanism for synchronizing various devices for performing automatic welding based on the signal. I have.

Here, whether or not an arc discharge has been formed between the welding rod and the work can be easily and reliably determined by monitoring the current flowing between the two. Like the potential difference between them, it is not affected by the distance between them, the atmospheric gas, etc., and a predetermined current is detected if a discharge is formed, and no current is detected if a discharge is not formed. .

For this reason, conventionally, in an automatic arc welding apparatus, a configuration for monitoring a current of an arc discharge (hereinafter, referred to as an arc current) and generating a WCR signal has been widely adopted. By judging the movement start time of the welding torch using the WCR signal, the discharge start time and the movement start time of the welding torch are synchronized, and stable welding quality can be ensured.

[0007]

The conventional automatic arc welding apparatus generally employs a configuration in which a WCR signal is generated by a welding current relay that is turned on and off in accordance with the flow and interruption of an arc current. Have been. Therefore, when switching the WCR signal from on to off or from off to on, the relay is instructed to switch its state, and then the WCR signal is actually turned on.
There is a predetermined delay time before the CR signal is switched.

[0008] Conventionally, this delay time is
The time when the WCR signal switches from off to on (on delay) is about 22 to 26 ms, and the time when the WCR signal switches from on to off (off delay) is 170 to
It is set to about 230 ms.

In this case, the reason why the on-delay is set to be short is that it is necessary to accurately detect the start of arc discharge, and the reason why the off-delay is set to be long is not necessarily that of the WCR signal. This is because the stop time of the arc discharge can be accurately detected even if it is not determined.

That is, the detection of the start time of the arc discharge is performed by
As described above, the monitoring of the WCR signal has to be relied on, but the stop time of the arc discharge can be more accurately known by monitoring the control signal for instructing the stop of the arc current. Furthermore, if the off-delay is made as short as the on-delay, the WCR signal is too sensitive to changes in the arc current, making the signal difficult to use for control.

In consideration of these circumstances, for the welding current relay that generates the WCR signal, as described above, good response is given priority to the on-delay in a short time, and for the off delay, the WCR signal is generated. It is set for a relatively long time to give priority to stability.

However, in the above conventional method,
Once the arc current exceeds the predetermined value and the WCR signal is turned on, the WCR signal will not be turned off unless the arc current continues to fall below the predetermined value for the time exceeding the above-described 170 to 230 ms off delay.

Therefore, when a current exceeding a predetermined value once flows through the welding rod at the start of welding and the arc discharge is not properly formed thereafter, the welding torch moves even though the arc discharge is not formed. As a result, the desired welding quality cannot be ensured.

A typical example of such a phenomenon is a stick phenomenon at the start of arc welding. The stick phenomenon is a phenomenon that occurs relatively frequently at the start of welding in an automatic arc welding apparatus, and is a phenomenon in which when a welding rod supplied with a high voltage and a work are short-circuited, the welding rod does not explode and does not shift to arc discharge. is there. For example, it occurs due to poor grounding of a workpiece to constitute a discharge circuit, poor power supply to a welding rod, oxidation of the welding rod, or the like.

When the stick phenomenon occurs, the distance between the welding rod and the workpiece is short while they are short-circuited, that is, 5 mm.
Current flows only for about 0 to 70 ms. Then, no current flows for about 100 to 150 ms until the exploded welding rod contacts the workpiece again and short-circuits.

Here, 100 to 150 ms, which is the time during which the arc current is stopped by the stick phenomenon, is shorter than 170 to 230 ms of the above-mentioned WCR signal off-delay. Therefore, in the above-described conventional apparatus, even when the stick phenomenon occurs continuously a plurality of times, the WCR signal is transmitted as a continuous signal, which has just caused the above-described poor welding quality.

For this reason, when using the automatic arc welding apparatus according to the above-mentioned conventional configuration, it is necessary to carry out an appearance inspection or the like to prevent the outflow of defective workpieces. There was a problem that it could not be fully demonstrated.

The present invention has been made in view of the above points, and when an arc generation confirmation signal is turned on, it is determined whether or not arc discharge is normally formed based on the arc voltage. An object of the present invention is to provide an automatic arc welding method capable of solving the above-mentioned problem by moving a welding torch only when arc discharge is normally formed.

[0019]

FIG. 1 shows a principle diagram of an automatic arc welding method which can achieve the above object.

That is, the object of the present invention is to measure a current flowing between a welding rod and a workpiece to be welded, and to turn on an arc generation confirmation signal when the current value is equal to or more than a predetermined threshold. In the automatic arc welding method for moving the carriage for transferring the welding rod toward the welding end position when the arc generation confirmation signal is on, FIG.
As shown in (A), a first process for monitoring the voltage difference between the welding rod and the workpiece when the arc generation confirmation signal is turned on, and the potential difference is generated when an arc discharge is formed.
A second process for measuring a subsequent duration after the voltage reaches a value equal to or higher than the voltage to be generated, and a third process for instructing the carriage to start moving when the measured time reaches a predetermined determination time. Achieved by performing automatic arc welding methods.

Further, as shown in FIG. 1B, the arc generation confirmation signal is turned on and the potential difference between the welding rod and the workpiece is monitored following the first process for monitoring the potential difference. A fourth process for accumulating a time when a voltage that cannot occur at the time of arc discharge formation and a fifth process for determining that an abnormality has occurred in welding quality when the accumulated time reaches a predetermined determination value are executed. The automatic arc welding method described above is also effective for achieving the above object.

[0022]

In the automatic arc welding method having the structure shown in FIG. 1A, when the welding rod and the work are short-circuited to start welding, a predetermined current flows between the welding rod and the work. The arc is generated and the arc generation confirmation signal is turned on.

In this case, if a proper arc discharge is formed after the welding rod and the arc are short-circuited, an appropriate potential difference is generated between the two according to the dielectric breakdown of the atmospheric gas. On the other hand, if a proper arc discharge is not formed after the short circuit, the welding rod and the work are insulated by the atmospheric gas, so that the pressure is once increased to the power supply voltage, and then short-circuited again. Step down to ground level.

The first process monitors the potential difference between the welding rod and the workpiece after the generation of the arc generation confirmation signal, that is, after the first short circuit has occurred. Therefore, if the potential difference is maintained at a higher voltage than the voltage generated when the arc discharge is continuously formed, it can be determined that the arc discharge is formed normally. It can be determined that the discharge is not formed normally.

Here, in the second process, a duration time during which the voltage monitored in the first process is maintained at or above a voltage level generated when an arc discharge is formed is measured. And
The third process issues an instruction to start the movement of the carriage after it is determined that the arc discharge has been reliably formed for a duration exceeding a predetermined time.

In the fourth process, the time during which the voltage monitored in the first process is lower than the level that cannot occur at the time of arc discharge formation, that is, the short-circuit time generated after the first short-circuit occurs Is accumulated. In the fifth process, when the time accumulated in the fourth process reaches a predetermined time, it is determined that welding of the workpiece has not been properly performed and the welding quality is poor.

[0027]

FIG. 2 is a block diagram showing one embodiment of an automatic arc welding apparatus suitable for carrying out the automatic arc welding method according to the present invention.

In the figure, reference numeral 10 denotes a carriage which holds a welding torch 11. The carriage 10 can transfer the welding torch 11 in a predetermined direction with high precision by a lead screw driven by a motor.

The welding torch 11 is provided with a wire corresponding to a welding rod at the tip, and can feed this wire as required. The wire 12 is connected to the welding torch 1
1 is connected to the positive terminal 13 a of the welding power source 13, and the distal end of the wire 12 is connected to the positive terminal 1 of the welding power source 13.
It is kept at the same potential as 3a.

The negative terminal 13b of the welding power source 13 is
The negative electrode terminal 13 is connected to a workpiece 14 to be welded.
b and the work 14 are kept at the same potential. For this reason, when the tip of the wire 12 and the work 14 are separated from each other and no arc discharge is formed between them, a potential difference occurs between the positive terminal 13a and the negative terminal 13b therebetween. It will be.

In the figure, reference numeral 15 denotes a control panel,
0, a welding power source 13 and a detection unit 16 which is a main part of the present embodiment. here,
The welding power source 13 receives a start command supplied from the control panel 15, applies a voltage between the wire 12 and the work 14, and feeds the wire 12 at a constant speed to achieve a predetermined arc welding. Start or stop arcing.

On the other hand, the welding power supply 13 detects a current flowing through the wire 12 with a pickup coil or a Hall element or the like, and detects a current value flowing through a discharge circuit including the wire 12 and the work 14. When the current value exceeds a predetermined value, the built-in welding current relay is turned on to generate an arc generation confirmation signal (WCR signal). This WCR signal is supplied to the detection unit 16 as shown in FIG.

The welding power supply 13 of the present embodiment has a voltage detecting mechanism for detecting a voltage generated between the positive terminal 13a and the negative terminal 13b, that is, an arc voltage generated between the wire 12 and the work 14. Have. Then, the detected arc voltage is supplied to the detection unit 16 together with the WCR signal.

The detection unit 16 generates a predetermined control signal to be described later based on the WCR signal and the arc voltage supplied from the welding power source 13 and supplies the control signal to the control panel 15. Based on these signals, the control panel 15 issues a movement command to the carriage 10 to execute appropriate arc welding and performs a process for preventing defective products from flowing out, as described later.

The operation of the present embodiment will be described below. Prior to that, the necessity of the processing executed by the present embodiment will be described.

FIG. 3 shows a configuration diagram of a welding apparatus for performing a conventionally known automatic arc welding method. The conventional welding apparatus shown in FIG. 3 does not include the detection unit 16 shown in FIG. 2, and is different from the above-described apparatus in that the WCR signal generated by the welding power source 13 is directly input to the control panel 15. Other configurations are the same. Hereinafter, the operation of the conventional automatic arc welding apparatus will be described with reference to the time chart shown in FIG.

FIG. 4A shows a state where the welding power source 13 is supplied from the control panel 15.
5 shows a signal of an arc start command transmitted toward.
This signal is the signal to command the start and end of arc discharge.
The high level is the discharge command and the low level is the discharge stop command.
is there. Accordingly, in FIG. ₁Signal is high
When the bell is reached, the welding power source 13 receives the
A predetermined voltage is applied between the wire 12 and the work 14 to start
Pressure is applied and the wire 1
Start feeding 2.

As a result, the wire 12 and the work 14 are short-circuited with a predetermined potential difference, causing dielectric breakdown, and arc discharge is started. Then, when the arc start command becomes low level at time t ₄ , the welding power supply 13 stops the application of the voltage to stop the discharge and stops the feeding of the wire 12.

FIG. 4B shows a WC generated by the welding power source 13.
The R signal is shown. That is, when the arc start command is issued at time t ₁ and the discharge is formed as described above, a current exceeding a predetermined value flows through the wire 12. In response, the welding current relay built in welding power supply 13 is turned on after a predetermined on-delay (time t ₂ ), and accordingly, the WCR signal goes high.

When the arc current disappears at time t ₄ , the welding current relay is turned off after a predetermined off-delay (time t ₅ ), and the WCR signal switches to low level.

The on-delay and the off-delay are considered in consideration of the high-speed response required for the WCR signal and the ease of handling when used as a control signal.
In this embodiment, the on-delay is 22 to 26 ms and the off-delay is 17 ms, similarly to the conventional apparatus shown in FIG.
It is set to 0 to 230 ms.

FIG. 9C shows a timer for detecting an arc break at the start, which is incorporated in the control panel 15. This timer is cleared by a WCR signal notifying the occurrence of arc discharge. The control panel 15 issues an arc start command at time t ₁ and starts counting by this timer. Then, if the WCR signal is not supplied within T ₁ second, it is determined that the arc break at the start is abnormal.

Therefore, when the welding torch 11 does not properly feed the wire 12, when the welding power source 13 does not generate a predetermined voltage, or when the discharge circuit formed by the welding power source 13, the wire 12 and the work 14 is disconnected. If such an abnormality occurs, the abnormality is detected, and the defective welding work caused by the abnormality does not flow out.

FIG. 4D shows the operation state of the halfway arc break detection circuit for detecting a case where the arc discharge is started once and the arc is broken halfway. When a high-level WCR signal is transmitted from the welding power source 13 (time t _{2 in} the figure), the circuit starts operating in response to the high-level WCR signal until the arc start command becomes a low level (see FIG. A)
Time t ₄ ) The WRC signal is constantly monitored.

If any abnormality occurs during this period and the WCR signal goes low after a predetermined off-delay, it is determined that an arc break has occurred during welding and an abnormality signal is output. Accordingly, the abnormality of the arc break is also detected, and the outflow of the work of poor quality can be prevented.

FIG. 7E shows the storage state of the arc generation storage circuit. . As shown in the figure, this storage state is excited by the input of the WCR signal (time t _{2 in} the figure) and until the arc start command is inverted to a low level at the end of machining (in the figure, (A) Time t ₄ ) That state is maintained.

That is, this signal is not affected by the state of the discharge circuit or the like, and maintains a high level from the time when the discharge is started to the time when the discharge should be completed. Therefore, when it is desired to transport the carriage 10 to the home position and wait when an abnormality occurs, the carriage 10 is always transported based on the arc generation storage signal, so that the carriage 10 is always driven regardless of the abnormality after the start of welding. It can be transported to a predetermined position.

FIG. 9F shows a movement command signal for controlling the transfer of the carriage holding the welding torch and the like. This signal is transmitted from the control panel 15 to the carriage 10, and its start timing and end timing are both set based on the above-mentioned arc generation storage signal. That is, the occurrence of arc discharge is stored at time t _2, the response to this first operation delay timer operates.

The operation delay timer is set to count up at a time T ₂ expected to be required until a stable arc discharge is formed, for example, about 0.1 to 0.3 seconds. It is a timer. Then, the rising movement command signal and the set time T ₂ has elapsed, the movement command is set to be maintained until the arc stored is released.

Therefore, the carriage 10 carrying the welding torch 11 starts moving after a predetermined time T ₂ after the rise of the WCR signal (time t ₂ ), and then determines whether or not welding is normally performed. regardless, it would be sure to continue the movement until the time t ₄ when processing is completed.

The current flowing through the wire 12 (hereinafter referred to as wire current) in the apparatus of the present embodiment shown in FIG. 2 and the conventional apparatus shown in FIG.
4 (hereinafter referred to as wire voltage) and WCR
The signal indicates a relationship as shown in the time chart of FIG. 5 or FIG.

FIG. 5 shows a waveform when the arc discharge is normally started in response to the arc discharge start command. At time t _{1 in} FIG. 5, the welding torch 1
1 is the time when the wire 12 and the work 14 are short-circuited.

Therefore, in FIG. 5, the wire current sharply increases at time t ₁ (FIG. 5A), and the wire voltage sharply decreases to almost 0 V (FIG. 5B). Thereafter, in the case where the wire 12 and the workpiece 14 are normally separated from each other by arc melting and the arc discharge normally proceeds, the wire current gradually decreases as the distance between the two increases (see FIG. 5A). , Period), and eventually reaches a predetermined reference current value (time t ₃ ). Then, the flow of a predetermined current is started, and the wire 12
About 20 to 80 ms after the short circuit between the workpiece and the work 14, a stable arc discharge is formed.

In the apparatus of this embodiment, a pulse current having a cycle of 5 ms to 10 ms is superimposed on the base current as shown in FIG. For this reason,
At the time of arc discharge, the melted portion at the end of the wire 12 is atomized due to the pinch effect due to the pulse current and adheres to the work 14 to obtain a good bead. In this case, the wire voltage is constant because the discharge gap is constant.
Although FIG. 5B shows a straight line, there is no large fluctuation regardless of the superposition of the pulse current.

On the other hand, as shown in FIG. 5 (C), after the wire current becomes equal to or more than the predetermined current, the WCR signal becomes 22-26.
It goes high after the on-delay of ms elapses. Therefore, when 0.1 to 0.3 ms elapses and the operation delay timer counts up, a movement command is transmitted from the control panel 15 to the carriage 10, and the movement of the welding torch 11 is started.

As described above, normal arc discharge is started 20 to 80 ms after the wire 12 and the work 14 are short-circuited.
It is possible to reliably perform welding from the start of the movement of the workpiece, and to secure welding quality that conforms to the standard.

On the other hand, as shown in FIG. 6, when the stick phenomenon occurs at the start of the arc discharge, the movement of the carriage 10 is started before a normal arc discharge is formed between the wire 12 and the work 14. In some cases, desired welding quality cannot be ensured at the beginning of welding.

That is, at time t ₁ in FIG. 6A, the wire 12 and the work 14 are short-circuited, and when a short-circuit current of 50 to 70 ms flows, the wire 12 explodes and does not normally shift to arc discharge. Even if the WCR signal is
As shown in (C), after a predetermined on-delay (time t ₂ ), the level becomes high.

The exploded wire 12 is connected to the welding torch 1
100 to 150 ms after being sent to the work 1 again
It reaches the position where it is short-circuited with 4. Therefore, when the stick phenomenon occurs continuously, even though the short circuit between the wire 12 and the work 14 is merely repeated, W
A situation occurs in which the CR signal is not inverted to a low level.

In this case, since the control panel 15 in the conventional welding apparatus issues a movement command assuming that the arc discharge is normally performed, as shown in FIG. In some cases, a defective workpiece having a defective defective bead 14b was formed.

Therefore, in the apparatus of the present embodiment shown in FIG. 2, a detection unit 16 is provided in order to prevent the defective work from flowing out by the automatic arc welding apparatus. Hereinafter, the operation of the apparatus of this embodiment will be described in detail focusing on the operation of the detection unit shown in FIG.

FIG. 8 shows the detection unit 16 and the welding power source 13.
And a block diagram showing a connection state with the control panel 15.
As shown in FIG. 2 and FIG. 2, a WCR signal and an arc voltage signal are supplied to the detection unit 16 from the welding power source 13. A power cable for supplying power to the detection unit 16 is also connected between them. On the other hand, a carriage start signal described later is supplied from the detection unit 16 to the control panel 15 as a control signal.

By the way, the detection unit 16 performs the above-described first to third processing by executing processing according to a flowchart shown in FIG. 9, for example. That is, as shown in FIG. 9, an arc start command is output from the control panel 15 to the welding power source 13 to start the arc welding, and the process is started. In step 100, it is determined whether or not the WCR signal is received. I do.

When the welding power source 13, the welding torch 11, etc. are operating normally and a predetermined WCR signal is received, the process proceeds to step 110, where the WCR signal and the arc voltage signal supplied from the welding power source 13 at predetermined time intervals are set. And monitor. On the other hand, when the WCR signal is not received, step 100 is repeatedly executed until the WCR signal is received.

In the present embodiment, step 110
Is set to 4 ms. Thus, in step 110, the above-described voltage monitoring process, that is, the first process is executed.

When the WCR signal and the arc voltage are detected in the current processing, the routine proceeds to step 120, where it is determined whether or not the WCR signal is maintained on and the arc voltage is a predetermined voltage, for example, 10 V or more.

Here, the monitoring of the WCR signal is temporarily
If the CR signal is off, it means that some abnormality has occurred in the welding power supply 13 or the discharge circuit, or that the welding has been completed and the arc discharge has disappeared. This is because there is no need to execute the processing of.

Also, 10 V in the above step is
The voltage is sufficiently lower than the arc voltage when arc discharge is formed in the apparatus of the present embodiment. Therefore, the case where the WCR signal is on and the arc voltage has not reached the predetermined voltage (10 V) means that no arc discharge was formed between the short-circuited wire 12 and the work 14 due to the stick phenomenon or the like. This is the case (period and in FIG. 10).

Therefore, if the WCR signal is turned on and the arc voltage is not higher than 10 V in step 120, the process returns to step 110 and steps 110 and 120 are repeatedly executed until the condition is satisfied. If it is determined that the condition is satisfied, step 1
Proceed to 30.

In step 130, it is determined whether or not such conditions are continuously satisfied for a predetermined time T. Even when the stick phenomenon occurs, the condition is satisfied while the wire 12 and the work 14 are separated (period in FIG. 10). This is because it cannot be determined that the phenomenon has not occurred. As described above, the steps 120 and 130 correspond to the high-pressure duration measurement described above,
That is, the second process is executed.

Therefore, if it is determined in step 130 that T seconds have not elapsed since the condition was satisfied, steps 110 to 130 are repeatedly executed until T seconds are satisfied. That is, the WCR signal and the arc voltage are detected every 4 ms, and if they satisfy a predetermined condition, 4 ms is added to the duration, and the WCR signal and the arc voltage are added until the result becomes T seconds. Continue monitoring.

When it is determined that the above-mentioned predetermined condition is satisfied for a continuous T seconds (time t _{1 in} FIG. 10),
Proceeding to step 140, the carriage start signal (FIG. 10D) is set to the high level, assuming that the arc discharge has been reliably formed between the wire 12 and the work 14. The contents of step 140 correspond to the above-described movement start instruction, that is, the third processing.

Therefore, if the movement command supplied from the control panel 15 to the carriage 10 is generated based on the carriage start signal, the arc discharge is surely started when the movement of the carriage 10 is started. Can be secured.

Therefore, the control panel 15 of this embodiment is different from that of FIG.
By controlling various signals etc. in a time chart as shown in
It is ensured that the movement of the carriage 10 is started after the arc discharge is formed without damaging the abnormality detection mechanism provided in the conventional automatic welding device.

That is, as shown in FIG. 11 (A), when an arc start command is issued at time t ₁ , the counting of the starting arc-out detection timer is started at the same time (FIG. 11 (C)). Then, a carriage start signal supplied from the detection unit 16 is used in place of the conventional WCR signal (FIG. 11B).

Here, it is essential that a WCR signal be received in order for the carriage start signal to be issued as shown in FIG. 9 (step 10 in FIG. 9).
0) If no WCR signal is generated, no carry start signal is generated. Therefore, if the arc current does not flow normally after the arc start command is issued due to the abnormality of the welding power source 13 or the welding torch 11, the predetermined time T at which the start-time arc-out detection timer is counted up.
_The carriage start signal is not received within ₁ and the start-up arc breakage abnormality is detected in the apparatus of this embodiment as in the conventional apparatus.

Similarly, when the once generated WCR signal is interrupted during welding, the carry start signal is inverted to a low level. Therefore, if the operation of the halfway arc break detection circuit shown in FIG. 11D is started based on the carriage start signal, it is possible to detect the halfway arc breakage abnormality similarly to the conventional apparatus.

Then, as shown in FIG. 11 (F), the movement command signal for commanding the movement start of the carriage 10 adopts a configuration which rises in synchronization with the carriage start signal, so that the movement of the carriage 10 is surely caused by the arc discharge. It is to be started after the start. In this case, the carry start signal directly indicates the start of arc discharge as described above. For this reason, the WCR
There is no need to consider the time lag between the rise time of the signal and the time at which the arc discharge is actually formed, and there is an advantage that it is not necessary to use a delay time timer when raising the movement command signal.

[0079] Further, in this embodiment, across from the carriage start signal is not incoming even if not formed successfully arc discharge by using the stick phenomenon or the like, the setting time T ₁ of the such abnormal start arc interruption detection timer If the abnormality continues, the abnormality can be detected as an arc break abnormality at the start.

Therefore, when the stick phenomenon continues for a long period of time and the wire 14 and the work 14 are repeatedly short-circuited at the welding start position of the work 12, an abnormality is reliably detected, and thereafter the stick phenomenon is detected. Even if it converges, such a work is not welded and flown out as a normal product.

FIG. 12 is a block diagram showing another embodiment of an automatic arc welding apparatus suitable for carrying out the automatic arc welding method according to the present invention. In this figure, the same components as those of the embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

That is, the apparatus of the present embodiment includes the detection unit 17 which is different from the above embodiment as a main part, and outputs the WCR signal generated by the welding power source 13 in addition to the detection unit 17.
It is characterized in that it also enters the control panel 15.

Further, as shown in FIG. 13, the detection unit 17 of this embodiment is operated by the electric power supplied from the welding power source 13 and performs a predetermined process based on the WCR signal and the arc voltage signal. 2, and is characterized in that a bead missing abnormality signal is supplied to the control panel 15.

More specifically, as is apparent from the operation time chart of the apparatus of this embodiment shown in FIG. 14 and the operation time chart of the conventional apparatus shown in FIG. Bead missing signal (Fig. 14
Except for the intervention of (G)), the same operation as the conventional device is performed.

That is, the apparatus according to the present embodiment estimates the quality of the performed welding based on the WCR signal supplied from the welding power source 13 to the detecting unit 17 and the arc voltage signal, and judges the quality of the performed welding. This prevents outflow of defective work.

Hereinafter, the operation will be described with reference to FIG. 15 which is a flowchart of an example of processing executed by the detection unit 17 of this embodiment. Note that the detection unit 17 of the present embodiment executes the processing according to the flowchart shown in FIG.
Is a unit that executes the processing of.

That is, when an arc start command is output from the control panel 15 to the welding power source 13, step 2
At 00, it is determined whether or not a WCR signal has been received.
When the WCR signal is received, the process proceeds to step 210, in which a monitoring time timer in which a time for monitoring the presence or absence of an abnormality after the start of welding is set, and whether or not the timer has counted up is determined.

Here, the monitoring time timer is set to monitor the abnormality only at the beginning of welding. The failure due to the stick phenomenon or the like often occurs immediately after the start of welding, and the failure occurs at the beginning of welding. This is because if an abnormality occurs, it is sufficient to treat it as poor quality regardless of whether or not the later stage of welding is normal.

Therefore, if it is determined that the monitoring time timer has already counted up, the process is terminated. If it is determined that the timer has not yet counted up, the process proceeds to step 220 to monitor the WCR signal and the arc voltage. Note that the processing contents of step 220 correspond to the contents of the above-described first processing, and are set so as to be performed at predetermined time intervals, for example, at every 4 ms.

After detecting the WCR signal and the arc voltage in step 220, it is determined in step 230 whether the WCR signal is on and the arc voltage is equal to or lower than a predetermined voltage. The predetermined voltage is required to be sufficiently lower than the arc voltage when the arc discharge is formed and sufficiently higher than the wire voltage when the wire 12 and the work 14 are short-circuited, for example, 10 V The degree is suitable.

Therefore, the condition for determining the feasibility in step 230, that is, the condition in which the WCR signal is on and the arc voltage is equal to or lower than the predetermined voltage (10 V), means that the wire 12 and the work 14 are short-circuited after the WCR signal rises. This is a condition that indicates In other words, this is a condition that does not hold in principle when arc discharge is normally formed between the wire 12 and the work 14.

That is, when the condition of step 230 is satisfied for a long time or repeatedly, it can be determined that the arc discharge is not normally formed. Therefore, in the present embodiment, if the condition is not satisfied in the step 230, the steps 220 and 23
0 is repeated, and only when it is determined that the condition is satisfied, the routine proceeds to step 240, and the accumulated time is calculated by adding 4 ms this time to the time when the condition was satisfied in the past.
Thus, the above-described fourth processing is executed in steps 230 and 240.

At step 250, it is determined whether or not the accumulated time has reached a predetermined determination time T. If the time has reached T, it is determined that an abnormality has occurred, and at step 260, a bead missing abnormality signal Was output. Steps 250 and 260 correspond to the above-described fifth processing.

Therefore, according to the present embodiment, if an arc discharge is properly formed at the start of welding, steps 220 to 250 are repeatedly executed, and the detection unit 17 may generate a bead missing abnormality signal. Absent.
On the other hand, when an arc discharge failure due to a stick phenomenon or the like occurs continuously beyond a predetermined level, a bead missing abnormality signal is reliably sent from the detection unit 17 to the control panel 15.

For this reason, unlike the conventional automatic arc welding apparatus, the bead missing abnormality that causes insufficient welding in the initial stage of welding can be detected on the control panel 15 side, and by performing an appropriate process such as displaying an abnormality, the defective workpiece can be detected. Outflow can be reliably prevented.

In the process of this embodiment, the wire 12
The abnormality determination is not performed until the accumulated value of the short circuit time between the workpiece and the workpiece 14 reaches T because the movement command of the carriage 10 is started after a predetermined operation delay timer counts up. That is, as shown in FIG. 14, after the WCR signal is received by the control
_During the period ₂ , the carriage 10 does not move, and it is considered that the arc discharge failure during this period does not affect the welding quality.

[0097]

As described above, according to the first aspect of the present invention, the formation of an arc discharge due to a stick phenomenon or the like occurring at the beginning of automatic arc welding is monitored by monitoring the potential difference between the welding rod and the workpiece. , And the movement start timing of the welding torch can be appropriately controlled. Therefore, the automatic arc welding method according to the present invention has a feature that the outflow of defective workpieces can be reliably prevented by synchronizing the timing when the arc discharge is reliably formed and the timing when the movement of the welding torch is started. doing.

According to the second aspect of the present invention, the formation of an arc discharge is detected based on the potential difference between the welding rod and the workpiece, and the formation is continued to such an extent that the defect affects the welding quality. In this case, it can be determined that the workpiece quality is poor. Therefore, the automatic arc welding method according to the present invention has a feature that it is excellent in preventing outflow of defective workpieces, similarly to the invention of the first aspect.

[Brief description of the drawings]

FIG. 1 is a principle diagram of an automatic arc welding method according to the present invention.

FIG. 2 is a configuration diagram of an embodiment of an automatic arc welding apparatus suitable for carrying out the present invention.

FIG. 3 is a configuration diagram of a conventional automatic arc welding apparatus.

FIG. 4 is a time chart for explaining the operation of a conventional automatic arc welding apparatus.

FIG. 5 is a diagram for explaining the necessity of the present invention (part 1)
It is.

FIG. 6 is a diagram for explaining the necessity of the present invention (part 2);
It is.

FIG. 7 is a perspective view showing an appearance of a defective work in a conventional automatic arc welding apparatus.

FIG. 8 is a block diagram illustrating a main part of the apparatus according to the present embodiment.

FIG. 9 is a flowchart illustrating an example of a process performed by the apparatus according to the embodiment.

FIG. 10 is a diagram for explaining the operation of the apparatus according to the embodiment.

FIG. 11 is a time chart for explaining the operation of the apparatus of this embodiment.

FIG. 12 is a configuration diagram of another embodiment of an automatic arc welding apparatus suitable for carrying out the present invention.

FIG. 13 is a block diagram showing a main part of another embodiment of the present invention.

FIG. 14 is a time chart for explaining the operation of another embodiment of the present invention.

FIG. 15 is a flowchart illustrating an example of a process performed by the apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Carriage 11 Welding torch 12 Wire 13 Welding power supply 14 Work 15 Control panel 16, 17 Detection unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-200380 (JP, A) JP-A-1-293975 (JP, A) JP-A-58-188571 (JP, A) JP-A-63-1988 212069 (JP, A) JP-A-4-105768 (JP, A) JP-A-6-126454 (JP, A) JP-A-3-23067 (JP, A) JP-A-5-8038 (JP, A) JP-B-63-65434 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) B23K 9/00 B23K 9/095 B23K 9/127

Claims (2)

(57) [Claims] A current flowing between a welding rod and a workpiece to be welded is measured, and when the current value is equal to or greater than a predetermined threshold, an arc generation confirmation signal is turned on and the welding rod is transferred. In an automatic arc welding method for moving a carriage toward a welding end position when the arc generation confirmation signal is on, the voltage monitoring between the welding rod and the workpiece is performed while the arc generation confirmation signal is on. And measuring the time during which the voltage is continuously maintained at a value equal to or higher than the voltage generated at the time of arc discharge formation , and starts moving the carriage when the measured time reaches a predetermined determination time. An automatic arc welding method characterized in that: 2. A current flowing between a welding rod and a workpiece to be welded is measured, and when the current value is equal to or greater than a predetermined threshold, an arc generation confirmation signal is turned on, and the welding rod is transferred. In an automatic arc welding method for moving a carriage toward a welding end position when the arc generation confirmation signal is on, the voltage monitoring between the welding rod and the workpiece is performed while the arc generation confirmation signal is on. And accumulating the time when the voltage becomes a voltage that cannot occur during the formation of arc discharge. When the accumulated time reaches a predetermined determination value, it is determined that an abnormality has occurred in welding quality. Automatic arc welding method.